The Changes Of Leaf Vein Network Structure And Photosynthetic Characteristics Of Three Robinia Pseudoacacia Types Under Drought Stress

Robinia plants have the characteristics of fast growth,drought resistance,thinness,strong resistance,economic value and wide ecological value.At present,there are original species of Robinia pseudoacacia,strong resistance;variegated Robinia pseudoacacia var.decaisneana Carr,red color,high ornamental value;new excellent variety Robinia pseudoacacia 'Anhui locust No.1',fast-growing without thorns,trunk straight.With the frequent global drought,there is a higher demand for improving the drought resistance and photosynthetic capacity of plants.Vein is an important water transport system in plant leaves.It is of great significance to study the relationship between leaf vein network structure and plant photosynthetic characteristics.In this study,three Robinia pseudoacacia types of Robinia pseudoacacia var.decaisneana Carr,Robinia pseudoacacia 'Anhui locust No.1',Robinia pseudoacacia.were used as research materials,and the leaf structure,gas exchange,water conductivity and water use efficiency of the Robinia pseudoacacia types after different water treatments were studied.The effects of drought stress on leaf structure,photosynthetic characteristics and water use efficiency,and the relationship between leaf structure and secondary vein structure on photosynthetic characteristics and water use efficiency.The main findings are as follows:(1)When the soil is deficient in water due to drought,the plant will undergo a series of changes:the leaf area is reduced,and the leaf weight is increased;The stomatal density increases and the pore length decreases;the secondary vein density increases,the secondary vein diameter decreases;the water potential and water conductivity decrease;stomatal conductance,transpiration rate,net photosynthetic rate and water use efficiency decrease.At the same time,the leaf maintains water transport and gas exchange through the increase of secondary pulse density and diameter,which is beneficial to slow down the decline of photosynthesis ability of plants and maintain a certain photosynthetic capacity;the leaves increase the density of secondary veins and reduce the diameter to ensure a certain moisture.Supply,maintain stomatal movement,increase stomatal density,reduce length,and flexibly regulate water,which is beneficial to improve water use efficiency of plants.(2)When drought stress occurred,there was a significant negative correlation between stomatal density and stomatal length.There was a significant negative correlation between pulse density and secondary pulse diameter.There was a significant positive correlation between stomatal density and secondary pulse density.Plants responded to drought through drought-induced changes in leaf structure.(3)Photosynthetic capacity and water use efficiency of three Robinia pseudoacacia species,under normal water conditions,in turn for:R.pseudoacacia var.decaisneana Carr.>R.pseudoacacia 'Anhui locust No.1'>Robinia pseudoacacia.;under drought stress,in order:Robinia pseudoacacia.>R.pseudoacacia 'Anhui locust No.1'>R.pseudoacacia var.decaisneana Carr.Different types of hedgehogs have different productivity and different drought resistance.Therefore,when carrying out afforestation management,it is necessary to consider the respective growth characteristics.